The center-back is unpopular under Ange Postecoglou at Spurs, but his former manager in Italy might provide him a first-team position.
Dier has fallen out of favour at the north London club and has not played a single minute of football under Ange Postecoglou this season.
And according to Tuttosport, Dier is Mourinho’s top choice as the former Spurs manager seeks to strengthen his back line in January.
The 29-year-old has also earned 49 England caps and scored three goals for his country.
At Tottenham, he has played as a defensive midfielder and a center defender, but Postecoglou prefers players with speed in his squads, thus he has lost favor.
His contract expires at the end of the current campaign, thus Roma or any other prospective suitors are unlikely to incur significant costs should they decide to move in January.